Device for reducing power consumption of optical drive and method for the same

ABSTRACT

A device and method for reducing power consumption of an optical drive are proposed. The present invention samples a carrier control signal and then compares the samples of the signals with predetermined threshold signals. According to the comparison result, the present invention increases or decreases an output signal index. The variation of the output signal index is used to control phases of diphase excitation control signals so as to control the rotation direction of a motor or make it stop. The present invention need not output the diphase excitation control signals continuously. It only needs to output a predetermined number of the diphase excitation control signals after the output signal index is increased or decreased. Hence, the present invention reduces the time for outputting the control signals and greatly reduces the power consumption of the optical drive thereby.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to a device for reducing powerconsumption of an optical drive and a method for the same, and moreparticularly, to a device and a method used to reduce the power consumedin track following so as to conserve power.

2. Description of Related Art

In the optical drives used nowadays, track following is an action thatconsumes an extreme amount of time and power. However, this action mustbe fast enough to improve access speed. Since this action is performedin many applications, various searching algorithms available on themarket have been developed to make this action more efficient. However,the power consumption thereof is still excessive.

Reference is made to FIG. 1, which illustrates the track-followingsignals used nowadays. The sinusoidal wave is a carrier control signal202. The conventional method is to obtain specific sample voltages 205at some specific sample times 204 and then output these sample voltages205 as diphase excitation control signals 206. Every diphase excitationcontrol signal 206 will maintain its voltage value until the nextsampling time 205 to control the rotation direction of the carrier motoror to stop it.

In the present invention, a novel track-following method is proposed toreplace the conventional one to save power and further-promoteefficiency.

SUMMARY OF THE INVENTION

An objective of the present invention is to provide a device and methodfor reducing power consumption of an optical drive. The presentinvention digitally processes a carrier control signal provided by acarrier controller and compares the processed signal with twopredetermined threshold voltages. Subsequently, it inputs a signal intoa waveform generator according to the comparison result and outputslow-power periodic excitation signals to control a power actuator so asto make a carrier motor rotate forward, rotate reversely or stop.Thereby, the pickup head can be moved to the correct optical track.

For reaching the objective above, the present invention employs a signalprocessor, a comparator and a waveform generator to form the sampledcontrol signals and reduce power consumption.

Numerous additional features, benefits and details of the presentinvention are described in the detailed description, which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will be more readily appreciated as the same becomes betterunderstood by reference to the following detailed, description, whentaken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a diagram for illustrating track-following control signals ofan optical drive in the prior art;

FIG. 2 is a diagram of a preferred embodiment of a device for reducingpower consumption of an optical drive in accordance with the presentinvention;

FIG. 3A is a diagram of an internal structure of the signal controllerin accordance with the present invention;

FIG. 3 b is a diagram of an internal structure of the carrier controllerin accordance with the present invention;

FIG. 4 is a waveform diagram of diphase excitation control signalsprovided by the waveform generator in accordance with the presentinvention;

FIG. 5 is a waveform diagram of an output signal index provided by thecomparator in accordance with the present invention;

FIG. 6A is a waveform diagram of diphase excitation control signalsformed by using a group of gain signals in accordance with the presentinvention;

FIG. 6B is a waveform diagram of diphase excitation control signalsformed by using two groups of gain signals in accordance with thepresent invention; and

FIG. 7 is a flowchart of a method for reducing power consumption of anoptical drive in accordance with the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention relates to a device for reducing power consumptionof an optical drive and a method for the same. Reference is made to FIG.2, which is an embodiment of the present invention. The device includesa signal controller 100, an access controller 120, a signal processor140, a comparator 150, a waveform generator 160, a power actuator 170and a carrier motor 180. After the signal controller 100 receives atrack-following error signal (TE) and a central error signal (CSO), itoutputs a track-following control signal (TRO), which is sent to theaccess controller 120 and used to control the pick-up head 130 to reador write the data.

The signal controller 100 outputs a carrier control signal 108 to thesignal processor 140, which samples the carrier control signal 108 andsend the sampled carrier control signal 144 to the comparator 150. Thecomparator compares the sampled carrier control signal 144 with thepositive threshold signal (P-th) 152 and the negative threshold signal(N-th) 154 and then sends out an output signal index. If the sampledcarrier control signal 144 is larger than the positive threshold signal152, the comparator 150 adds one to the output signal index. If thesampled carrier control signal 144 is smaller than the negativethreshold signal 154, the comparator 150 subtracts one from the outputsignal index. The waveform generator 160 outputs the diphase excitationcontrol signals 162 (FMO and FMO2) periodically with equal time spacingaccording to the output signal index sent from the comparator 150. Asthe output signal index increases or decreases, the phases of thediphase excitation control signals 162 changes accordingly so as tocontrol the power actuator 170. Then, the power actuator 170 generatesthe complementary motor control signals to make the carrier motor 180rotate forward or backward, or make it stop so as to control the pickuphead 130 thereby.

Reference is made to FIG. 3A, which is a diagram of an internalstructure of the signal controller in accordance with the presentinvention. The signal controller includes a track-following errorcontroller 102, a carrier controller 104 and amplifiers 114, 118. Afterthe track-following error controller 102 receives the track-followingerror signal (TE), it outputs the track-following control signal (TRO)accordingly. Then, the track-following control signal is delivered tothe access controller 120 and the amplifier 114. The carrier controller104 then selectively sends out the track-following control signal (TRO)or the central error signal (CSO). In other words, the carrier controlsignal 108 can be the track-following control signal (TRO) or thecentral error signal (CSO).

If the track-following control signal (TRO) is selected, the amplifier114 diminishes the same to avoid signal overflow caused by the carriercontroller 104. Then, the amplifier 118 recovers the amplitude of thetrack-following control signal (TRO) when the track-following controlsignal (TRO) is output from the carrier controller 104.

Reference is made to FIG. 3B. The carrier controller 104 is composed ofa first low-pass filter 1041 cascaded with a second low-pass filer 1043.The first low-pass filter 1041 has a high sample rate while the secondlow-pass filter 1043 has a low sample rate.

Reference is made to FIG. 4, which shows the diphase excitation controlsignals produced by the waveform generator 160. The vertical axisrepresents voltage value while the horizontal axis represents time. Thesinusoidal wave 301 corresponds to the carrier control signal 108mentioned above and the periodic signals 303 are the output signals ofthe waveform generator 160. The periodic signals 303 are generated bysampling the carrier sample signal 108, i.e., the sampled carriercontrol signals 144, after the comparator 150 processes these samplesignals. When compared with the sinusoidal signal used in the prior art,using the periodic signals 303 can reduce the power consumption of theoptical drive. The use of the periodic signals 303 will be furtherillustrated in FIG. 6A.

After receiving the carrier control signal 108, the signal processor 140samples the carrier control signal 108 according to the predeterminedsample rate and the corresponding time spacing 305. The sample rate canbe the sample rate of the second low-pass filter 1043 mentioned above.The carrier control signal 108 is sampled at the sample time 302 toprovide the sampled carrier control signal 144 for the comparator 150.Then, the comparator 150 compares the sampled control signal 144 withthe positive threshold signal 152 and the negative threshold signal 154.

Reference is made to FIG. 5, which is an embodiment of the presentinvention. In the figure, the vertical axis represents the increment ofthe output signal index output from the comparator 150 while thehorizontal axis represents the threshold voltage. If the sampled carriercontrol signal 144 is larger than the positive threshold signal 152, thecomparator 150 adds one to the output signal index. If the sampledcarrier control signal 144 is smaller than the negative threshold signal154, the comparator 150 subtracts one from the output signal index. Ifthe sampled carrier control signal 144 is located in the middle betweenthe positive threshold signal 152 and the negative threshold signal 154,the output signal index is maintained.

Reference is made to FIG. 6A, which is an embodiment of the presentinvention. The increase of the output signal index means the sampledcarrier control signal 144 is larger than the positive threshold signal152. At this point, the waveform generator 160 samples the carriercontrol signal 108 continuously according to the waveform of the carriercontrol signal 108 and outputs a predetermined number of impulse signals309 with equal time spacing 307. These impulse signals 309 are thediphase excitation control signals 162 mentioned above. The increase ofthe output signal index makes the motor 180 rotate forward. On the otherhand, the decrease of the output signal index means the sampled carriercontrol signal 144 is smaller than the negative threshold signal 154 andmakes the motor 180 to rotate backward by the same mechanism describedabove.

The sample rate of the diphase excitation control signals 162 can be thesample rate of the first low-pass filter 1041. Since the first low-passfilter 1041 has a high sample frequency and the second low-pass filter1043 has a low sample frequency, the time spacing 305 of the carriercontrol signal 108 is larger than the time spacing 307 of the diphaseexcitation control signals 162. After that, the waveform generator 160does not produce any signal and the power actuator 170 maintainsoperations according to the previous diphase excitation control signals162.

Generally, the power consumption is proportional to the output time ofthe diphase excitation control signals 162. In the present invention,the sinusoidal wave 301, i.e., the carrier control signal, is sampled toprovide the periodic signals 303, which are composed of the impulsesignals 309 and can be used as the diphase excitation control signals162. Furthermore, the sample number is adjustable.

Comparing the diphase excitation control signals 162 shown in FIG. 6A tothe diphase excitation control signal 206 shown in FIG. 1, it is seenthat the diphase excitation control signals 162 of the present inventioninclude several periodic signals 303 each having a predetermined numberof impulse signals 309, which are the samples of the sinusoidal wave301. Furthermore, the control signal 206 of the prior art is formed bysampling the carrier control signal 202 and then keeping the samplevoltage value until the next sampling time. Since the diphase excitationcontrol signals 162 of the present invention do not need to last for thewhole period of the sinusoidal wave 301 to control the rotation of thecarrier motor 180, power consumption is greatly reduced. Thus, theexcitation control signals 162 of the present invention only need tolast for a small segment of the whole period to control the carriermotor 180. That not only saves the electric power considerably but alsomaintains the operation of the carrier motor 180 efficiently.

In FIG. 6A, the waveform generator 160 employs a group of gain signalsto adjust the positive edges of the impulse signals 309. The waveformgenerator 160 directly drops the amplitude of the negative edges to zerorather than using the gain signals to adjust them. Since the diphaseexcitation control signal 162 is composed of multiple impulse signals309, the stability of the pickup head 160 is affected because the hugevariation of the impulse signals 309 makes the motor 180 vibrate easily.

Therefore, the present invention also provides another embodiment. Asshown in FIG. 6B, the impulse signals 309 shown in FIG. 6A are replacedby the impulse signals 311. The waveform generator 160 in thisembodiment employs two groups of gain signals to adjust the positive andnegative edges of the impulse signals 311, respectively. Hence, thenegative edge of the impulse signal 311 does not drop to zero directlybut to the middle, between the amplitude of the positive edge and zero.Thus, the vibration problem of the carrier motor 180 caused by theimpulse signals 309 is resolved.

When the carrier motor 180 moves the pickup head 130 to the correctoptical track, the central error signal (CSO) is zero, as is the carriercontrol signal 108. Hence, the output signal index sent from thecomparator 150 is unchanged and the waveform generator 160 stopsproducing the diphase excitation control signal 162. Meanwhile, thepower actuator 170 also stops producing the complementary motor controlsignals 174 so as to stop the carrier motor 180. Then, the pickup head130 starts to access data.

Reference is made to FIG. 7, which is a flowchart of a method forreducing power consumption of an optical drive in accordance with thepresent invention. The method includes the steps as follows. Thelocation of the pickup head is detected to calculate the distancebetween the pickup head and the target track (600). The central errorsignal, which represents the distance between the pickup head and thetarget track, is obtained (602). The carrier control signal is formed,by the carrier controller processing the central error signal, andoutput (604). The carrier control signal is sampled to obtain thesampled carrier control signal (606). The sampled carrier control signalis compared with the positive and negative threshold signals todetermine whether the sampled carrier control signal is larger than thepositive threshold signal (P-th) or smaller than the negative thresholdsignal (N-th), or just located between the positive and negativethreshold signals (608).

If the sampled carrier control signal is larger than the positivethreshold signal, the process jumps to step 610. If the sampled carriercontrol signal is smaller than the negative threshold signal, theprocess jumps to step 620. If the sampled carrier control signal islocated between the positive and negative threshold signals, the processjumps to step 630.

In the case where the sampled carrier control signal is larger than thepositive threshold signal, one is added to the output signal index.Then, due to the increase of the output signal index, the waveformgenerator 160 provides multiple predetermined diphase excitation controlsignals formed with equal time spacing to the power actuator. Afterfinishing sending the diphase excitation control signals, the waveformgenerator 160 stops providing the signals to reduce power consumptionand wait for the next diphase excitation control signals (612). Althoughthe waveform generator 160 stops providing the signals, the poweractuator keeps outputting the motor control signals to make the carriermotor rotate forward (614) according to the diphase excitation controlsignals received last.

In the case where the sampled carrier control signal is smaller than thenegative threshold signal, one is subtracted from the output signalindex (620). Then, due to the decrease of the output signal index, thewaveform generator 160 provides multiple predetermined diphaseexcitation control signals formed with equal time spacing to the poweractuator. When compared with the diphase excitation control signalsmentioned in the above paragraph, it is evident that the diphaseexcitation control signals at-this step have an opposite phase.

After finishing sending the diphase excitation control signals, thewaveform generator 160 stops providing the signals to reduce powerconsumption and waits for the next diphase excitation control signals(622). Although the waveform generator 160 stops providing the signals,the power actuator keeps outputting the motor control signals to makethe carrier motor rotate backward (624) according to the diphaseexcitation control signals received last.

In the case where the sampled carrier control signal is located betweenthe positive and negative threshold signals, the output signal indexremains unchanged (630). Hence, the output signal of the waveformgenerator 160 returns to zero and the power actuator stops outputtingmotor control signals to the carrier motor so as to stop the carriermotor. The steps above is performed repeatedly (650) to move the pickuphead to the correct access position.

Although the present invention has been described with reference to thepreferred embodiment thereof, it will be understood that the inventionis not limited to the details thereof. Various substitutions andmodifications have been suggested in the foregoing description, andother will occur to those of ordinary skill in-the art. Therefore, allsuch substitutions and modifications are embraced within the scope ofthe invention as defined in the appended claims.

1. A device for reducing power consumption of an optical drive,comprising: a signal controller for receiving a central error signal andproducing a carrier control signal; a signal processor for sampling thecarrier control signal to produce a first output signal; a comparatorfor receiving the first output signal of the signal processor andcomparing the output signal with a positive threshold signal and anegative threshold signal to produce a second output signal; and awaveform generator for receiving the second output signal of thecomparator and producing a periodic signal, the periodic signal beingformed by sampling a segment of the carrier control signal, wherein alocation of the segment is adjustable.
 2. The device as claimed in claim1, wherein the signal controller further comprises a track-followingerror controller and a carrier controller, the track-following errorcontroller receives a track-following error signal and produce atrack-following control signal, and the carrier controller receives thecentral error signal and the track-following control signal and outputone of them as the carrier control signal.
 3. The device as claimed inclaim 2, wherein before the track-following control signal is sent tothe carrier controller, the track-following control signal is diminishedby an amplifier to avoid signal overflow caused by the carriercontroller.
 4. The device as claimed in claim 3, wherein after thetrack-following control signal is passed through the carrier controller,the track-following control signal is amplified by another amplifier. 5.The device as claimed in claim 2, wherein the carrier controllerincludes a first low-pass filter and a second low-pass filter.
 6. Thedevice as claimed in claim 5, wherein the first low-pass filter has ahigh sample frequency and the second low-pass filter has a low samplefrequency.
 7. The device as claimed in claim 1, wherein the signalprocessor samples the carrier control signal to output a sampled carriercontrol signal.
 8. The device as claimed in claim 1, wherein the secondoutput signal sent from the comparator is an output signal index.
 9. Thedevice as claimed in claim 8, wherein the comparator adds one to theoutput signal index if the sampled carrier control signal is larger thanthe positive threshold signal, the comparator subtracts one from theoutput signal index if the sampled carrier control signal is smallerthan the negative threshold signal, and the comparator maintains theoutput signal index if the sampled carrier control signal is locatedbetween the positive threshold signal and the negative threshold signal.10. The device as claimed in claim 8, wherein the waveform generatoroutputs a predetermined number of periodic diphase excitation controlsignals having equal time spacing according to the output signal indexsent from the comparator.
 11. The device as claimed in claim 10, whereinphases of the diphase excitation control signals are changed as theoutput signal index is changed.
 12. The device as claimed in claim 10,wherein, after receiving the output signal index produced by thecomparator, the waveform generator samples the carrier control signaland then outputs a predetermined number of impulse signals to form thediphase excitation control signals.
 13. The device as claimed in claim10, wherein the waveform generator employs a group of gain signals toadjust positive edges of the diphase excitation control signals.
 14. Thedevice as claimed in claim 10, wherein the waveform generator employstwo groups of gain signals to adjust positive edges and negative edgesof the diphase excitation control signals, respectively.
 15. The deviceas claimed in claim 10, further comprising: a power actuator forreceiving the diphase excitation control signal and outputting twogroups of motor control signals according to the diphase excitationcontrol signal.
 16. The device as claimed in claim 15, furthercomprising: a carrier motor for receiving the two groups of the motorcontrol signals so as to move a pickup head to a correct optical track.17. The device as claimed in claim 16, wherein the two groups of themotor control signals are two groups of complementary signals.
 18. Amethod for reducing power consumption of an optical drive, comprising:inputting a carrier control signal to a signal processor; sampling thecarrier control signal to obtain a sampled carrier control signal byusing the signal processor; inputting the sampled carrier control signalto a comparator and comparing the sampled carrier control signal with apositive threshold signal and a negative threshold signal by using thecomparator; producing an output signal index according to a comparisonresult provided by the comparator; and outputting a predetermined numberof diphase excitation control signals having equal time spacingaccording to the output signal index by using a waveform generator. 19.The method as claimed in claim 18, further comprising: selecting eithera central error, signal or a track-following control signal as thecarrier control signal by using a carrier controller.
 20. The method asclaimed in claim 18, wherein phases of the diphase excitation controlsignals are changed as the output signal index is changed.
 21. Themethod as claimed in claim 18, wherein the signal processor samples thecarrier control signal according to a predetermined sample frequency.22. The method as claimed in claim 18, further comprising: adding one tothe output signal index if the sampled carrier control signal is largerthan the positive threshold signal.
 23. The method as claimed in claim22, wherein the waveform generator sends the diphase excitation controlsignals to a power actuator to make the power actuator produce twogroups of motor control signals so as to make a carrier motor rotateforward.
 24. The method as claimed in claim 23, wherein after finishingsending the diphase excitation control signals to the power actuator,the waveform generator stops sending the diphase excitation controlsignals and the power actuator keeps outputting the two groups of themotor control signals to make the carrier motor rotate forward accordingthe diphase excitation control signals received last.
 25. The method asclaimed in claim 18, further comprising: subtracting one from the outputsignal index if the sampled carrier control signal is smaller than thenegative threshold signal.
 26. The method as claimed in claim 25,wherein the waveform generator sends the diphase excitation controlsignals to a power actuator to make the power actuator produce twogroups of motor control signals so as to make a carrier motor rotatebackward.
 27. The method as claimed in claim 26, wherein, afterfinishing sending the diphase excitation control signals to the poweractuator, the waveform generator stops sending the diphase excitationcontrol signals and the power actuator keeps outputting the two groupsof the motor control signals to make the carrier motor rotate backwardaccording the diphase excitation control signals received last.
 28. Themethod as claimed in claim 18, further comprising: maintaining theoutput signal index if the sampled carrier control signal is locatedbetween the positive and negative threshold signals.
 29. The method asclaimed in claim 28, wherein the waveform generator stops outputting thediphase excitation control signals to a power actuator to make the poweractuator stop outputting motor control signals to a carrier motor so asto stop the motor.
 30. The method as claimed in claim 18, wherein thewaveform generator employs a group of gain signals to adjust positiveedges of the diphase excitation control signals.
 31. The method asclaimed in claim 18, wherein the waveform generator employs two groupsof gain signals to adjust positive edges and negative edges of thediphase excitation control signals, respectively.